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Optical Engineering

Fringe pattern analysis for optical alignment in nanolithography using two-dimentional Fourier transform
Author(s): Feng Xu; Hu Song; Shaolin Zhou
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Paper Abstract

A simple but effective phase analysis method for the fringe pattern that occurs in two superposed grating marks applied in the previously designed dual-grating-based alignment scheme for lithography is proposed. First, the fringe pattern is processed and analyzed using a frequency domain method based on two-dimensional (2D) Fourier transform, and the 2D notch filter is appropriately designed to select the useful spectrum to obtain the target phase information. Further, phase difference of two sets of fringes is computed to acquire the alignment offset. Numerical simulation and experiment are both performed to verify this method. Finally, certain analysis about the error of phase difference extraction in the fringe pattern and precision of alignment are also presented. The results indicate that the background and noise of the fringe pattern can be efficiently filtered and target phase information can be extracted with high accuracy through this method.

Paper Details

Date Published: 1 August 2011
PDF: 7 pages
Opt. Eng. 50(8) 088001 doi: 10.1117/1.3609007
Published in: Optical Engineering Volume 50, Issue 8
Show Author Affiliations
Feng Xu, Institute of Optics and Electronics (China)
Hu Song, Institute of Optics and Electronics (China)
Shaolin Zhou, Institute of Optics and Electronics (China)

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